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August 2002 PM-Ozone Event

From August 11, 2002 to August 16, 2002 the Northeast US experienced a significant regional transport/stagnation pollution event that resulted in elevated levels of ozone, PM2.5, and other secondary pollutants. This event was one of the most severe experienced in this area within the last decade. The following material documents various aspects of the event, including ground-based and high-elevation pollution measurements, meteorological information, satellite pictures, and related material.

PM Map

The following is based on a running 6-hour average of hourly PM2.5 data with 10 ug/m3 concentration isopleths.

High-Resolution Ozone Maps

The following are the Canadian versions [1-hour 20 ppb isopleths] of EPA's AIRNow ozone maps.

(courtesy of AIRNow)

Event Onset at the Summit of Mt. Washington, NH

This focuses on a rather unusual and interesting event onset on August 11 on the summit of Mt. Washington. All times are UTC (EDT +5).

The following preliminary plots are provided courtesy of AIRMAP.

Satellite Photos Over Northeast U.S.

Here are some satellite photos for August 12-14 provided by Land Rapid Response System. Notice that for August 14th there are indications of a fire present (i.e., red dots), including the fire at Old Fort Devens.

Below are some forward trajectory and concentration animations of the Devens fire on August 14th. Also below is a plot of the maximum ozone that was recorded on that day.

Boston Measurements

The following plot contrasts this event with the July 1999 haze event, as measured in Boston (same site, same method), data courtesy of Harvard School of Public Health (HSPH).

Sulfate and PM Chart for 3 Sites

Data from continuous PM2.5 and continuous sulfate measurements in Boston, MA (HSPH), the summit of Mt. Washington, NH, and Pittsburgh, PA.

August Meteorology

The following description provides meteorological context to the degradation of air quality across the region between August 8 and 15.

Surface Weather Maps

The linked sequence of surface weather maps shows the progression of weather system development across the continental U.S. in 12 hour increments. Maps courtesy of

Back Trajectories

The linked sequence of figures step through the august episode from the perspective of 48 hour back trajectories arriving 200, 500 and 1000 meters above ground level at 17 surface monitoring sites across the Northeast U.S. Back Trajectories were calculated using the HY-SPLIT trajectory model and correspond the same times as the surface weather maps above.

Upper Air Meteorology

Data from radar profilers operated within the region and output from the MM5 meteorological model are compared in the following set of graphs which show the wind speed and direction at various pressure heights throughout the lower atmosphere. (Profiler data courtesy NOAA; MM5 data courtesy University of Maryland).

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